Thermal Inactivation of Salmonella spp., Salmonella typhimurium DT104, and Escherichia coli O157:H7 in Ground Beef

In 19.1% fat ground beef, Escherichia coli O157:H7 was less heat- resistant at ≥58 °C than the Salmonella typhimurium DT104 and Salmonella senftenberg, but at 55 °C the D value was similar to DT104 strains and higher than an eight-strain Salmonella cocktail. Inactivation of E. coli O157:H7 was more temperature-dependent than the cocktail and DT104 strains. E. coli and DT104 strains were more heat-resistant in beef containing 19% fat than 4,8% fat. The cocktail was more thermally stable in stationary as compared to log phase. Freezing of inoculated raw meat decreased heat resistance of the cocktail. The pathogenic strain, growth phase of the organism, state of the meat (fresh or frozen) and meat composition must be considered when designing protocols to verify thermal processes. Cette etude determine la resistance thermique de Salmonella spp., Salmonella typhimurium DT104, et Escherichia coli O157:H7 dans des viandes de boeuf hachees a differents taux de matieres grasses. Les resultats indiquent que le type de pathogene, la phase de croissance, l'etat de la viande (fraiche ou congelee) et la teneur en matieres grasses doivent etre consideres lors de l'elaboration de protocoles de verification des procedes thermiques.